In recent years, polymers and plastics have become increasingly popular and important materials for making various types of articles. These articles, in turn, have been used in a limitless variety of applications. In some applications, the polymeric or plastic material, or an item contained in a polymeric or plastic article made therefrom is subject to attack and contamination by microorganisms. As such, a polymeric or plastic material capable of destroying or inhibiting foreign microorganisms would be desirable.
For instance, for the past three decades dentists have been warned that unusually high levels of microorganisms may be inhabiting dental unit water lines. Some of these microorganisms have been found to be pathogenic, meaning that they are capable of causing disease. This potential problem has recently been given great attention due to the increased number of immuno-compromised people caused in part by the spread of the HIV virus.
Dental unit water lines are particularly susceptible to invasion by microorganisms. These water lines are typically connected to a municipal water supply which contains very low levels of bacteria. However, when the water remains stagnant in the line, for instance overnight or over a weekend, bacteria will attach themselves to the polymer tubing and multiply. The resulting bacteria layer is known as a biofilm, a microbial mass attached to a surface that is bathed in liquids. Dental unit water lines have a very high surface area in proportion to the amount of water running through the lines which further promotes biofilm growth. Of course, biofilms can plague other polymeric articles, including household faucet lines, shower curtains, bathtub liners, garbage bags, surgical liners, tubing in air conditioners, or even artificial implants.
When present in dental unit water lines, the biofilms can separate from the tubing wall during operation causing bacteria to flow into a patient's mouth. Normally, a patient would not be susceptible to infection or disease unless the patient is immunity deficient. However, the potential always exists for infection.
In the past, solutions aimed at eliminating the biofilm problem have included flushing the line before each use. However, the water pressure in the line is typically not great enough to remove biofilms attached to the tubing walls. Further, because water flows in layers with the fastest moving layer being in the middle, the layer in contact with the tubing or the biofilm is stationary or slow moving. Although flushings will remove microorganisms loosely attached to the biofilm, it will not solve the greater biofilm problem.
Another proposed solution is to use water from an independent and sterile water source. However, such systems are expensive and also, through time, may become contaminated. Biofilms may develop if water lines are not flushed daily or the valves in the system maintained. Specifically, check valves would have to be installed into the system to ensure that used water is not retracted into the sterile water line.
Other suggestions to solve the biocide problem in dental tube lines have included the addition of filters or the use of chemical disinfectants. However, filters fail over time and cannot be easily monitored. Chemical disinfectants, on the other hand, may damage the equipment over time. Also, once biofilms are established, they are very resistant to disinfectants.
The present invention is concerned with solving the biofilm problem in dental tubing and overcoming the deficiencies of the above-suggested solutions. In general terms, the present invention relates to polymeric materials containing anti-microbial agents. The materials further include chemical controllers for controlling the rate of anti-microbial migration. In a particular application for dental tubing, anti-microbial agents and the chemical controllers are mixed with polymer compositions during formation of the tubing.
The anti-microbial agents contained within the tubing thereafter destroy the bacteria in the water flowing through the tube while the chemical controllers regulate the rate of release of the anti-microbial agents. The chemical controllers also ensure that the biocidal activity within the dental tube remains active for a substantial period of time and that large amounts of the anti-microbial agents are not released at once. Of course, dental tubing is only one specific application for the composition of the present invention.
The prior art discloses a number of examples of plastic materials containing biocidal materials but none have the particular characteristics of the present invention. For instance, U.S. Pat. No. 4,888,175 to Burtone et al., which is incorporated herein by reference in its entirety, discloses a plastic packaging material having a biocidal agent dissolved or dispersed therein. The biocidal agent used is 10,10-oxybisphenoxarsine which is an organically bound arsenic and will be referred to hereinafter as OBPA. The plastic material can be formed into a package for containing an organic material susceptible to bacterial or viral attack, such as plants, or the material may be formed in the shape of a dispensable liner for bathtubs.
U.S. Pat. No. 4,666,956 to Spielau et al. discloses a biocidal composition based on organic arsenic compounds. A tin compound is added to the composition to prevent elution of the arsenic compound. The compositions are used in the production of molded plastic articles, especially those vulnerable to biological attack.
U.S. Pat. Nos. 4,624,679 and 4,891,391, both to McEntee, disclose an anti-microbial and anti-oxidant composition preferably incorporated into a thermoplastic resin. The anti-microbial agents are incorporated into the thermoplastic materials during fabrication so that the resulting thermoplastic articles will resist microbial growth. The anti-oxidant is added so that the anti-microbial agent does not degrade during processing. OBPA is disclosed as one of the microbiocides.
An assortment of compositions containing microbiocides are disclosed in U.S. Pat. Nos. 4,686,239, 4,789,692, 4,086,297, and 4,663,077 in which Rei is listed as the inventor or one of the inventors. In the '239 patent, the '692 patent, and the '297 patent, a composition is disclosed wherein a microbiocide in high concentrations is added to a thermoplastic resin. The resulting concentrate is then incorporated into a second thermoplastic resin to produce a resulting article having the appropriate level of microbiocide. The second thermoplastic resin is added in an attempt to control the mobility of the microbiocide. One of the microbiocides disclosed is OBPA.
The '077 patent discloses a microbiocidal solution comprising an aryl alkanol solvent and a microbiocide compound dissolved therein. A plasticizer suitable for use as a polymer processing aid is added to the composition.
Sanitary covers for use on telephones and the like are disclosed in U.S. Pat. No. 4,570,038 to Tinelli. This sanitary cover includes an anti-microbial material for preventing transfer of bacteria or the like from the telephone to the user. The cover can be made from a plastic while the anti-microbial material may include OBPA.
Anti-bacterial materials and anti-microbial mixtures are disclosed in United Kingdom Patent No. 1,169,288 and European Patent Application No. 84113170.9. The United Kingdom patent is directed to a material having a base Sheet of plastic coated on one surface with a polymeric liquid composition containing an anti-bacterial agent capable of migrating through the sheet. The European patent application, on the other hand, discloses a mixture of a phenoxyarsine as an anti-microbial agent and a solvent. A plasticizer can be added to the mixture for incorporation into plastics.
Other prior art compositions containing biocides include U.S. Pat. No. 4,747,902 to Saitoh, U.S. Pat. No. 3,864,468 to Hyman et al., U.S. Pat. 4,666,706 to Farguharson et al., U.S. Pat. No. 5,063,706 to Aki et al., and U.S. Pat. No. 4,876,070 to Tsukahara et al.
Although the prior art shows a combination of biocidal compositions, the particular features of the present invention are absent from the prior art. Some of the prior art discloses materials containing small amounts of biocidal compositions for preventing bacterial attack on the material itself. However, most of the prior art does not show the use of biocidal materials in packaging films or sheets at a level such that the contents of the package, instead of the plastic itself, are inhibited against bacterial or viral growth. Further, the prior art is generally deficient in affording a composition that will not only control bacterial growth but that will also simultaneously control the growth of fungi. The prior art is also deficient in providing a polymeric composition containing anti-microbial agents wherein the rate of migration of the anti-microbial agents is controlled.
Although it is known to incorporate anti-microbial agents into plastics, the plastic products generally cannot be used for food and medical packaging applications unless extremely small amounts of biocide are used. However, small quantities of biocide will not protect the contents of the package adequately or protect the contents for an effective length of time from attack. Consequently, a need exists for a polymeric material containing anti-microbial agents wherein the rate of migration of the anti-microbial agents is controlled such that high dosages of the biocide are not released. Also, a need exists for a composition containing anti-microbial agents wherein the anti-microbial agent are released over an extended period of time. Further, a need exists for an anti-microbial composition that will inhibit the growth of bacteria and also fungi, viruses, and actinomycetes as well.